FIELD OF THE INVENTION
The present invention relates, in general, to vibration testing apparatus and, more specifically, to apparatus and methods for detecting excessive vibrations in rotating internal combustion engines, such as those commonly used in vehicles automobiles and trucks.
A sensor is typically mounted on each engines for detecting vibrations caused by the interference or clearance between the various rotating and reciprocating parts of the engines. The output from the sensor is analyzed to determine whether the vibrations are indicative of a good or faulty enging. However, the sensor output and analyzed data merely provides an average value for the total vibrations caused by all of the rotating and reciprocating components of the engine during a pre-determined time period such as one firing cycle or rotation of the engine. Such previously devised testing apparatus do not identify the location in the engine where the vibration is occurring.
In rotating internal combustion engines, vibrations are typically caused by misalignment or excessive clearance between rotating and reciprocating components. Such vibrations are intensified during the detonation of the spark plug in each cylinder of the engine. It is known that certain problems, such as rod knock or piston slap, produce vibrations at different frequencies. However, previously devised testing apparatus merely average such frequencies over the entire engine firing cycle and do not provide any differentiation between the individual cylinders of the engine. Thus, the engine as a whole is accepted or rejected and, if rejected, there is no indication provided to the location of the source of the excessively high vibrations.
Thus, it would be desirable to provide a vibration testing apparatus which overcomes the problems encountered with previously devised vibration testing apparatus insofar as providing an indication of the source of the excessive vibrations in the engine. It would also be desirable to provide an engine vibration testing apparatus suitable for use with internal combustion engines which provides an indication of which cylinder in the engine any excessive vibrations are being generated. It would also be desirable to provide a vibration testing apparatus which could be used on engines of varying cylinder numbers. It would also be desirable to provide such a vibration testing apparatus which is usable for different locations of the vibration sensor on the engine. Finally, it would be desirable to provide a vibration testing apparatus which adjusts the pre-set reference vibration levels for varying engine speeds.